Dopamine D2 receptor blockade differentially affects the light‑adapted turtle and frog electroretinogram.

Area of Science:

• Neuroscience
• Ophthalmology
• Comparative Physiology

Background:

• Dopamine pathways in the retina modulate visual processing.
• Dopamine D2-class receptors play a role in retinal function.
• Electroretinography (ERG) is a key tool for assessing retinal function.

Purpose of the Study:

• To investigate the effects of dopamine D2-class receptor blockade using sulpiride on retinal function.
• To compare the impact of sulpiride on electroretinographic (ERG) responses in turtles and frogs.
• To elucidate species-specific differences in dopamine-mediated retinal pathways.

Main Methods:

• Light-adapted turtle (Trachemys scripta elegans) and frog (Rana ridibunda) eyecups were used.
• Electroretinograms (ERGs) were recorded following sulpiride administration at varying concentrations (40 μM, 120 μM, 240 μM).
• Analysis focused on the b-wave (ON response) and d-wave (OFF response) amplitudes, maximal voltage range, relative sensitivity, and absolute sensitivity.

Main Results:

• In turtles, 240 μM sulpiride increased b- and d-wave amplitudes; lower doses were ineffective.
• In frogs, sulpiride caused a dose-dependent decrease in b- and d-wave amplitudes.
• While maximal voltage range was affected in both species, absolute sensitivity was reduced only in frogs; time characteristics remained unchanged.

Conclusions:

• Dopamine D2-class receptor-mediated pathways exhibit significant species-specific differences between turtle and frog retinas.
• Sulpiride's differential effects highlight distinct roles of these receptors in ON and OFF pathway signaling.
• These findings advance our understanding of comparative retinal neurobiology and dopamine's role in visual processing.